Installing AIM on Mac OSX Version 10.4.8

So, I recently got a new macbook pro and I need help installing AIM on my Mac. When I go to AIM.com, I click download AIM and it downloaded aim.bin to my computer. When I click on it, it opens up microsoft excel and says "The operation could not be completed. An unexpected error occured (error code- 10660)" Any help would be appreciated.